1. Field of the Invention
The present invention relates to a quality inspection apparatus for a double-sided printing machine capable of printing opposite faces of a sheet-like material, and, more particularly, to a quality inspection apparatus for a double-sided printing machine which enables double-sided quality inspection without necessity of increasing installation space.
2. Description of the Related Art
An example of a conventional double-sided printing machine is a four-color double-sided simultaneous offset printing press as shown in FIG. 7 (see Japanese Patent No. 2612594).
In a printing unit 100 of the main unit, a rubber impression cylinder 101 having a paper gripping apparatus and a rubber cylinder 102 having no paper gripping apparatus are supported substantially horizontally such that the circumferential surfaces of the cylinders 101 and 102 are in contact with each other.
Four plate cylinders 103 are disposed along the circumferential surface of the rubber impression cylinder 101; and four plate cylinders 104 are disposed along the circumferential surface of the rubber cylinder 102. Inking units 105 and 106 are movably disposed such that the inking units 105 and 106 can approach and separate from the plate cylinders 103 and 104, respectively. The inking units 105 and 106 can supply ink and water to the plate cylinders 103 and 104 in a state in which the inking units 105 and 106 are in contact with the plate cylinders 103 and 104.
Meanwhile, a delivery cylinder 108 of a delivery unit 107 is disposed below the rubber impression cylinder 101. A chain 109 is disposed on the left Bide of the delivery cylinder 108 as shown in FIG. 7, such that the chain 109 does not cross a space below the position at which the circumferential surface of the rubber impression cylinder 101 is in contact with that of the rubber cylinder 102.
Further, transfer cylinders 111 to 114 each having a paper gripping apparatus are provided in order to transfer paper from a register 110 to the rubber impression cylinder 101; and a transfer cylinder 115 having a paper gripping apparatus is provided in order to transfer paper from the rubber impression cylinder 101 to the delivery cylinder 108. In FIG. 7, reference numeral 116 denotes a feeder unit.
Accordingly, a sheet of paper fed from the feeder unit 116 and positioned by the register 110 is conveyed along a path indicated by arrows in FIG. 7; i.e., is conveyed along the circumferential surfaces of the transfer cylinders 111 to 114, the circumferential surface of the rubber impression cylinder 101, the circumferential surface of the transfer cylinder 115, and the circumferential surface of the delivery cylinder 108, in this sequence. When the sheet of paper passes through the contact point between the rubber impression cylinder 101 and the rubber cylinder 102 from the upper side to the lower side of the contact point, the opposite faces of the sheet of paper undergo printing simultaneously.
Incidentally, when bank notes are printed by use of the above-described four-color double-sided simultaneous offset printing press, quality control is of particular importance. Therefore, conventionally, bank notes have been inspected manually by a large number of workers in an off-line fashion.
Recently, in order to save labor needed for inspection, there has been a trend toward performing in-line inspect printing, by use of an image technique, for each of printing steps, such as an offset printing step, an intaglio printing step, and a numbering step, to thereby prevent poorly-printed paper from being fed to a subsequent step.
Presently, such an in-line printing-quality inspection apparatus is employed in intaglio printing presses, but is not employed in four-color double-sided simultaneous offset printing presses, in consideration of installation space.
For example, when double-sided quality inspection is to be performed after completion of double-sided printing but before paper delivery, a suction guide and an inspection camera must be disposed on each of the opposite sides of a paper delivery chain; i.e., two sets consisting of the suction guide and the inspection camera (one for the front face of paper, and one for the back face of paper) must be provided. In such as case, since the suction guide cannot be disposed on the gripper-bar side of the paper delivery chain (because of interference with gripper bars), one of the set for the front face and the set for the back face must be disposed while the paper delivery chain is inverted. This increases the length of the transport path, resulting in an increase in the size of the apparatus.